Energy exchange system and method

ABSTRACT

A system and method for heating water are provided. The system includes a first subcooler for receiving a first water flow, a second subcooler for receiving a second water flow, a first condenser in fluid communication with the first subcooler and the second subcooler for receiving water from both subcoolers, and a second condenser in fluid communication with the first condenser. The method involves receiving a flow of water, and transferring heat to the water using the system.

FIELD

The present invention relates generally to energy exchange anddistribution systems including heating, ventilation, air-conditioningand water heating, and more particularly relates to an energy exchangesystem for transparent incorporation into a water heating system.

BACKGROUND

It is known to employ energy exchange technologies in order to, forexample, recover excess heat energy from an air-conditioning system toprovide energy to heat water. Many examples of such heat-exchangetechnologies came about in the early 1980s which reflect the end of theenergy crises of the 1970s. It is interesting to note that theseheat-exchange technologies have not been generally adopted.

SUMMARY

In accordance with an aspect of the invention, there is provided asystem for heating water. The system includes a first subcooler forreceiving a first water flow. The first subcooler is configured totransfer heat to the first water flow at a first heat transfer rate. Thesystem also includes a second subcooler for receiving a second waterflow. The second subcooler is configured to transfer heat to the secondwater flow at a second heat transfer rate. The system further includes afirst condenser in fluid communication with the first subcooler and thesecond subcooler. The first condenser is configured to receive acombined water flow. The combined water flow includes the first waterflow from the first subcooler and the second water flow from the secondsubcooler. The first condenser is further configured to transfer heat tothe combined water flow at a third heat transfer rate. Furthermore, thesystem includes a second condenser in fluid communication with the firstcondenser. The second condenser is configured to receive the combinedwater flow from the first condenser. Furthermore, the second condenseris configured to transfer heat to the combined water flow at a fourthheat transfer rate

The first subcooler may be configured to transfer heat from a firstrefrigerant to the first water flow. The first condenser may beconfigured to transfer heat from the first refrigerant to the combinedwater flow.

The second subcooler may be configured to transfer heat from a secondrefrigerant to the second water flow. The second condenser may beconfigured to transfer heat from the second refrigerant to the combinedwater flow.

The system may further include a first evaporator and a secondevaporator. The first evaporator may be for evaporating the firstrefrigerant. The second evaporator may be for evaporating the secondrefrigerant.

At least one of the first evaporator and the second evaporator may beconfigured to receive waste heat from a chiller system.

The system may further include a first connector and a second connector.The first connector may be for connecting a cold water source to thefirst subcooler and the second subcooler to receive the water. Thesecond connector may be for connecting the chiller system to theevaporator for receiving the waste heat.

The second connector may be configured to receive a liquid.

The system may further include a first compressor and a secondcompressor. The first compressor may be for compressing the firstrefrigerant. The second compressor may be for compressing the secondrefrigerant.

The second compressor may compress the second refrigerant to a higherpressure than the first compressor compresses the first refrigerant.

The first condenser, the first subcooler, the first evaporator and thefirst compressor form a first refrigerant circuit.

The first refrigerant circuit may be a closed circuit.

The first portion of water may be equal to the second portion of water.

The first heat transfer rate, the second heat transfer rate, the thirdheat transfer rate, and the fourth heat transfer rate may becumulatively sufficient for increasing a temperature of the combinedwater flow by at least 30° C.

The first heat transfer rate, the second heat transfer rate, the thirdheat transfer rate, and the fourth heat transfer rate may becumulatively sufficient for increasing a temperature of the combinedwater flow by at least 40° C.

In accordance with an aspect of the invention, there is provided amethod of heating water. The method involves receiving, at a firstsubcooler, a first water flow. The method also involves transferringheat at a first heat transfer rate to the first water flow through thefirst subcooler. The method further involves receiving, at a secondsubcooler, a second the water flow. Furthermore, the method involvestransferring heat at a second heat transfer rate to the second waterflow through the second subcooler. In addition, the method involvesreceiving, at the first condenser, a combined water flow. The combinedwater flow includes the first water flow from the first subcooler andthe second water flow from the second subcooler. The method furtherinvolves transferring heat at a third heat transfer rate to the combinedwater flow through the first condenser. The method additionally involvesreceiving, at the second condenser, the combined water flow from thefirst condenser. The method further involves transferring heat at athird heat transfer rate to the combined water flow through the secondcondenser.

Transferring heat to the first water flow through the first subcoolerand transferring heat to the combined water flow through the firstcondenser may involve transferring heat from a first refrigerant.

Transferring the heat to the second water flow through the secondsubcooler and transferring heat to the combined water flow through thesecond condenser may involve transferring heat from a secondrefrigerant.

The method may further involve compressing the second refrigerant to ahigher pressure than the first compressor compresses the firstrefrigerant.

The method may further involve increasing a temperature of the water byat least 30° C. by transferring heat to the first water flow through thefirst subcooler, transferring heat to the second water flow through thesecond subcooler, transferring heat to the combined water flow throughthe first condenser, and transferring heat to the combined water flowthrough the second condenser.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example only, to the accompanyingdrawings in which:

FIG. 1 is a schematic representation of an exemplary energy exchangesystem in accordance with an embodiment;

FIG. 2 is a schematic representation of a heat recovery system inaccordance with an embodiment;

FIG. 3 is a schematic representation of water flow through the heatrecovery system of the embodiment shown in FIG. 2;

FIG. 4 is a schematic representation a subcooler in accordance with anembodiment;

FIG. 5 is a schematic representation a condenser in accordance with anembodiment;

FIG. 6 is a schematic representation of refrigerant flow through theheat recovery system of the embodiment shown in FIG. 2;

FIG. 7 is a graph showing the refrigerant/water temperature profile fora single condenser/subcooler pair;

FIG. 8 is a graph showing the refrigerant/water temperature profile inthe heat recovery system of the embodiment shown in FIG. 2;

FIG. 9 is a schematic representation of an exemplary energy exchangesystem in accordance with another embodiment;

FIG. 10 is a schematic representation of water flow through the heatrecovery system in accordance with another embodiment;

FIG. 11 is a schematic representation of water flow through the heatrecovery system in accordance with another embodiment; and

FIG. 12 is a schematic representation of refrigerant flow through theheat recovery system in accordance with another embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to FIG. 1, a schematic representation of an energyexchange system for transferring heat energy is shown generally at 50.It is to be understood that the energy exchange system 50 is purelyexemplary and that it will be apparent to those skilled in the art thata variety of energy exchange systems are contemplated. The energyexchange system 50 includes a chiller system 54, a hot water system 58,and a heat recovery system 62.

In the present embodiment, the chiller system 54 includes a heattransfer unit 66 and a cooling tower 70. It is to be appreciated, withthe benefit of this description, that chiller system 54 is notparticularly limited to any particular structural configuration and thatvariations capable of removing heat energy from a space arecontemplated. The foregoing description of the structure of the chillersystem 54 is intended to describe a cooling system that can be employedto provide a cooling system in a building such as a hotel, officebuilding, residential home, or industrial building having a plurality ofspaces, such as rooms. In particular, the chiller system 54 is generallyconfigured to remove heat energy from a space using the heat transferunit 66. The heat energy removed from the space is generally consideredto be waste heat and is generally expelled by the chiller system 54 atthe cooling tower 70 into another space such as the exterior of thebuilding where temperature is not controlled.

Accordingly, it is to be understood that the actual implementations ofthe chiller system 54 can vary according a number of variables,including the size of each space, the size and manufacturer of the heattransfer unit 66, and cooling tower 70. Therefore, notwithstanding thedescription provided, the specific embodiment for a given structure willbe expected to be different, and possibly substantially different, foreach and every structure. For example, although the present embodimentshown in FIG. 1 shows a single heat transfer unit 66, it is to beunderstood that the chiller system 54 can include a plurality of heattransfer units, each heat transfer unit being capable of independentcontrol. Independent control can provide for varying rates of heattransfer at each heat transfer unit to allow for a variation oftemperature across different spaces within a structure. In one example,independent variation and control of the temperature across differentspaces can provide for independent temperature control in differentrooms within a building while using a single chiller system 54.Similarly, although the present embodiment shown in FIG. 1 shows asingle cooling tower 70, it is to be understood that the cooling tower70 can include a plurality of cooling towers.

In the present embodiment, the hot water system 58 includes a boiler 74for heating water in a hot water tank 78. Similar to the chiller system54, it is to be appreciated that the hot water system 58 is notparticularly limited to any particular structural configuration and thatvariations capable of removing heat energy from a space arecontemplated. For example, the hot water system 58 can omit the hotwater tank 78 and instead be a tankless system where a heat sourceprovides hot water on demand. As another example, the boiler 74 can beanother heat source capable of heating water, or the boiler 74 can beomitted in embodiments where the heat recovery system 62 can supplysufficient heat energy to the hot water tank 78.

In general terms, the heat recovery system 62 is configured to transferat least a portion of the waste heat from the chiller system 54 to thehot water system 58. However, it is to be re-emphasized that thestructure shown in FIG. 1 is a schematic, non-limiting representationonly. For example, although a single chiller system 54 and one hot watersystem 58 are shown in FIG. 1, it is to be understood that the energyexchange system 50 can include a plurality of chiller systems and/or aplurality of hot water systems. In such embodiments, each chiller systemand/or hot water system can be configured to operate in a portion of abuilding or complex where a single chiller system and/or hot watersystem is not sufficient. Indeed, a plurality of differentconfigurations of energy exchange system 50 is contemplated herein.

It is to be appreciated, with the benefit of this description, that theheat recovery system 62 is generally configured to operate between thechiller system 54 and the hot water system 58. Without the heat recoverysystem 62, the chiller system 54 and the hot water system 58 can operateindependently to cool a space within a building and provide hot water,respectively. However, by independently operating the chiller system 54and the hot water system 58 without the heat recovery system 62, powerwould need to be supplied to each of the chiller system 54 and the hotwater system 58 independently, usually in the form of electricity forthe chiller system 54 and usually in the form of burning a fossil fuelsuch as natural gas or diesel for the hot water system 58. Bytransferring some of the waste heat generated in the chiller system 54to the hot water system 58, it is to be appreciated, that the amount ofpower required to heat the water using the boiler 74 would be reduced.Accordingly, the heat recovery system 62 can be installed in a buildinghaving existing systems with low costs since the existing equipment in abuilding does not need to be replaced. Furthermore, since the existingequipment is not replaced, reverting to the original configuration forheating water solely using the boiler 74 would be simple, such as duringa failure of the heat recovery system 62 or during a scheduledmaintenance requiring the heat recovery system 62 to be offline.

Referring to FIG. 2, a representation of the heat recovery system 62 caninclude a chiller connector 63 for connecting to the chiller system 54and a water connector 64 for connecting to the hot water system 58. Thechiller connector 63 to the chiller system 54 is generally configured toreceive waste heat from the chiller system 54. For example, the wasteheat can be transferred using a medium such as a liquid, forced air orthrough thermal conduction. The water connector 64 to the hot watersystem 58 can include a connection from the boiler 74 to the hot watertank 78. It is to be appreciated that in some hot water systems, theboiler 74 can be incorporated within the hot water tank 78 such that theheat recovery system 62 receives water directly from a cold water source(not shown) for delivery to the hot water tank 78. By providing thechiller connector 63 and the water connector 64, it is to be appreciatedthat the heat recovery system can be simply incorporated in a widevariety of buildings without the need for modifications to the existingchiller system 54 or the hot water system 58.

It is to be re-emphasized that the embodiment shown in FIG. 2 is purelyexemplary and that variations are contemplated. For example, it is to beappreciated that the chiller connector 63 and the water connector 64 areoptional and can be omitted in some embodiments of the heat recoverysystem 62. As another example, the chiller connector 63 has an inlet andan outlet for the waste heat and the water connector 64 has an inlet andan outlet. In other embodiments, the chiller connector 63 and the waterconnector 64 can be a plurality of connectors where the inlet and theoutlet are provided using separate connectors.

Referring to FIG. 3, a schematic representation showing the flow ofwater through an embodiment of the heat recovery system 62 is shown ingreater detail. In particular, FIG. 3 illustrates the flow of waterthrough the heat recovery system 62. It is to be understood that theheat recovery system 62 is purely exemplary and it will be apparent tothose skilled in the art that a variety of heat recovery systems arecontemplated including other embodiments discussed in greater detailbelow. The heat recovery system 62 includes a first subcooler 100, asecond subcooler 104, a first condenser 108, and a second condenser 112.

In general, the heat recovery system 62 is configured to receive waterfrom a water source 116 and add waste heat from another system, such asthe chiller system 54, to the water for increasing the temperature ofthe water. The water source 116 is not particularly limited. Forexample, the water source 116 can include a municipal water source. Inother embodiments, the water source 116 can be a well or water tower. Insome embodiments, the heated water can be provided to the boiler 74 forfurther supplemental heat energy if the heat exchange system 62 cannotprovide sufficient temperature or heat energy to the water at the raterequired due to a demand for hot water. Alternatively, the heat recoverysystem can be connected between the hot water tank 78 and the boiler 74such that prior to receiving the water from the water source 116, thewater can pass through the boiler 74 to receive supplemental heat energyif required. Upon entering the heat recovery system 62, the water isgenerally passed through the first subcooler 100, the second subcooler104, the first condenser 108, and the second condenser 112, where heatenergy is added to the water. The manner by which waste heat from thechiller system 54 is added to the water is not particularly limited. Inthe present embodiment, the first and second condensers 108, 112condense a gaseous refrigerant into a liquid. The heat energy releasedby the phase change is transferred to the water by thermal conduction.The first and second subcoolers 100, 104 transfer heat energy from theliquid refrigerant to the water by thermal conduction since the liquidrefrigerant is configured to be at a higher temperature than theincoming water. After the water has been heated, the heat recoverysystem 62 delivers the hot water to the hot water tank 78.

In the present embodiment, the first subcooler 100 is configured toreceive at least a portion of the water from the water source 116. Inparticular, the first subcooler 100 is configured to receive a flow ofwater therethrough. The manner by which the water from the water source116 is divided to provide the first subcooler 100 with a portion is notparticularly limited. For example, in the present embodiment, a teeconnector can be used to divide the flow of water from the water source116 into approximately equal portions. The first subcooler 100 isfurther configured to transfer heat to the portion of the waterreceived. The manner by which heat energy is transferred is notparticularly limited. For example, in the present embodiment, the firstsubcooler 100 can include a first compartment 120 through whichrefrigerant flows and a second compartment 124 through which water flowsas shown in FIG. 4. It is to be appreciated, with the benefit of thisdescription, that the temperature of the refrigerant is greater than thetemperature of the water for water heating purposes. Accordingly, as thewater and refrigerant are in thermal communication, the water willreceive heat energy from the refrigerant and increase in temperaturewhereas the refrigerant will give off heat energy and subcool.

The two compartments 120, 124 are separated by a wall 128 configured totransfer heat from the first compartment 120 to the second compartment124. The rate at which heat energy is transferred is not particularlylimited and can depend on several factors such as the material, size andgeometry of the wall 128, as well as the relative temperatures of thetwo compartments 120, 124. The wall 128 is constructed from materialswhich can separate the two compartments while providing high thermalconductivity. Some examples of suitable materials include copper,stainless steel, aluminum, and other materials of high thermalconductivity. The exact configuration of the two compartments 120, 124is not particularly limited. In the present embodiment, the twocompartments 120, 124 are configured such that the refrigerant and thewater flow in opposite directions. In other embodiments, theconfiguration of two compartments 120, 124 can be arranged such that therefrigerant and the water flow in the same direction. In furtherembodiments, more compartments can be added to form alternating layersof refrigerant flow and water flow. The two compartments 120, 124 canalso be configured to follow a tortuous route and may be provided withinternal fins or other protrusions to increase heat transfer efficiency.

It is to be re-emphasized that the structure shown in FIG. 4 is aschematic, non-limiting representation only and that variations arecontemplated. Since the oil in the refrigerant can be considered a toxinand the water flowing through the first subcooler 100 from the hot watersystem 58 contains potable water, additional features can be added toensure the separation to the first compartment 120 and the secondcompartment 124. For example, in other embodiments, the first subcooler100 can include a double walled and an air gap such that a leak in oneof the walls will allow water or refrigerant to leak to atmosphere butcontamination of the potable water is prevented. As another example,further embodiments can include an additional heat transfer mechanism(not shown) can be installed between the hot water system 58 and theheat recovery system 62 to transfer the waste heat recovered by the heatrecovery system 62 such that the additional heat transfer mechanism actsas an barrier to prevent contamination of the potable water.

Referring again to FIG. 3, the second subcooler 104 is configured toreceive at least a portion of the water from the water source 116similar to the first subcooler 100. In particular, the first subcooler100 is configured to receive a flow of water therethrough. The secondsubcooler is further configured to transfer heat energy to the portionof the water received similar to the first subcooler 100. It is to beappreciated that the second subcooler 104 is not particularly limitedand can be similar or identical to the first subcooler 100. It is to bere-emphasized that the present embodiment is a non-limiting embodimentand that the first subcooler 100 and the second subcooler 104 can bedifferent from described. For example, the first subcooler 100 and thesecond subcooler 104 can be of different sizes, from differentmanufacturers, of a different type.

It is to be appreciated, with the benefit of this description, that thewater from the water source 116 flows into each of the first subcooler100 and the second subcooler 104 in parallel. In the present embodiment,approximately half of the water from the water source 116 flows intoeach of the first subcooler 100 and the second subcooler 104. However,in other embodiments, the flow can be configured such that the amount ofwater flowing into the first subcooler 100 is more or less than theamount of water flowing into the second subcooler 104. For example, insituations where the first subcooler 100 and the second subcooler 104are each configured to transfer heat energy at a different rate, theamount of water flowing into each of the first subcooler 100 and thesecond subcooler 104 can be adjusted such that the temperature of thewater leaving each of the first subcooler 100 and the second subcooler104 is similar. However, in the present embodiment, the water from eachof the first subcooler 100 and the second subcooler 104 is combinedafter the water passes through the subcoolers 100, 104 and natural fluidmixing averages the temperature of the combined water flow. The mannerby which the water from the subcoolers 100, 104 is combined is notparticularly limited. For example, in the present embodiment, a teeconnector can be used receive the portions of water from each of thesubcoolers 100, 104 to combine at a single outlet.

The first condenser 108 is in fluid communication with both the firstsubcooler 100 and the second subcooler 104. The first condenser 108configured to receive the portion of water passing through the firstsubcooler 100 and the portion of water passing through the secondsubcooler 104. In particular, the first condenser 108 is configured toreceive a combined water flow therethrough. The manner by which thefirst condenser receives the water from the first subcooler 100 and thesecond subcooler 104 is not particular limited. In the presentembodiment, piping is used to combine the partially heated waterportions from the first subcooler 100 and the second subcooler 104 andsubsequently direct the water to the first condenser 108. The firstcondenser 108 is further configured to transfer more heat energy to thepartially heated from the first subcooler 100 and the second subcooler104. The manner by which heat energy is transferred is not particularlylimited. For example, in the present embodiment, the first condenser 108can include a first compartment 140 into which gaseous refrigerantenters and a second compartment 144 through which the water flows asshown in FIG. 5. It is to be appreciated, with the benefit of thisdescription, that the lower temperature of the water relative to thegaseous refrigerant causes the refrigerant to condense on the wall 148,which is configured to transfer heat energy between the firstcompartment 140 and the second compartment 144. The rate at which heatenergy is transferred is not particularly limited and can depend onseveral factors such as the material, size and geometry of the wall 148,as well as the relative temperatures of the two compartments 140, 144.Accordingly, this phase change releases heat energy from therefrigerant, which is transferred to the water to increase thetemperature of the water.

The wall 148 is typically constructed from materials which can separatethe two compartments while providing high thermal conductivity. Someexamples of suitable materials include copper, stainless steel,aluminum, and other similar materials. The exact configuration of thetwo compartments 140, 144 is not particularly limited. In the presentembodiment, the two compartments 140, 144 are configured such that therefrigerant and the water flow in opposite directions. In otherembodiments, the configuration of two compartments 140, 144 can beconfigured such that the refrigerant and the water flow in the samedirection. However, it is to be appreciated that since liquidrefrigerant is collected, gravity can be used to collect the liquidrefrigerant. In further embodiments, more compartments can be added toform alternating layers of refrigerant flow and water flow or a shelland tube type condenser can be used. The two compartments 140, 144 mayalso be configured to follow a tortuous route and may be provided withinternal fins or other protrusions to increase heat transfer efficiency.

The second condenser 112 in fluid communication with the first condenser108 and is configured to receive the combined water flow after heatenergy was by added the first condenser 108. The second condenser 112 isconfigured to transfer heat energy to the water similar to the firstcondenser 108 to further increase the temperature of the water. It is tobe appreciated that the second condenser 112 is not particularly limitedand can be similar or identical to the first condenser 108. It is to bere-emphasized that the present embodiment is a non-limiting embodimentand that the first condenser 108 and the second condenser 112 can bedifferent from described. For example, the first condenser 108 and thesecond condenser 112 can be different sizes, from differentmanufacturers, of a different type, such as a shell and tube condenser.

It is to be appreciated, with the benefit of this description, that thewater from the first subcooler 100 and the second subcooler 104 flowsthrough the first condenser 108 and then the second condenser 112 inseries. Accordingly each of the first condenser 108 and the secondcondenser 112, adds heat energy to the water to further increase thetemperature of the water prior to delivering hot water to the hot watertank 78. By adding heat energy to the water in steps, it is to beappreciated that the heat recovery system 62 can consume less energythan if the water were to be increased to the desired temperature in asingle step.

Furthermore, it is to be understood by a person of skill in the art andwith the benefit of this specification, that for a heat recoveryapplication the combined water flow into and out of each of thecondensers 108, 112 are typically fixed. In particular, the rate of thecombined water flow is generally determined by the size of the unit(i.e. 150 tons) because the product to be consumed is hot water. Inaddition, it is to be understood that the temperature of the combinedwater leaving each of the condensers 108, 112 can affect the efficiencyof the heat recovery system 62 such that a lower temperature leads to ahigher efficiency. However, in a heat recovery application, thetemperatures of the combined water leaving each of the condensers 108,112 are generally fixed by the temperature at which hot water isdemanded.

In general terms, the heat recovery system 62 is generally configured toadd heat energy to water from a water source 116 and deliver it to thehot water tank 78. It is to be re-emphasized that the structure shown inFIGS. 3 to 5 is a non-limiting representation only. Notwithstanding thespecific example, it is to be understood that other mechanicallyequivalent structures and heat transfer mechanisms can be devised toperform the same function as the heat recovery system 62. For example,the manner by which waste heat is collected from the chiller system 54is not particularly limited. In general, the refrigerant is configuredto receive heat energy from the chiller system 54 and transferred to thewater using various different system configurations which will bediscussed in greater detail below.

Referring to FIG. 6, a schematic representation showing the flow ofrefrigerant through the embodiment of the heat recovery system 62 isshown in greater detail. It is to be re-emphasized that the heatrecovery system 62 is purely exemplary and it will be apparent to thoseskilled in the art that a variety of configurations are contemplatedincluding other embodiments discussed in greater detail below. In thepresent embodiment, the heat recovery system 62 includes a firstrefrigerant circuit 200 and a second refrigerant circuit 204. In thepresent embodiment, each of the first refrigerant circuit 200 and thesecond refrigerant circuit 204 is a closed circuit such that the amountof refrigerant in each of the first refrigerant circuit 200 and thesecond refrigerant circuit 204 is separated and does not leave or enterthe first refrigerant circuit 200 and the second refrigerant circuit204.

The first refrigerant circuit 200 includes the first subcooler 100, thefirst condenser 108, a first evaporator 208, and a first compressor 216.The first refrigerant circuit 200 is generally configured to transferheat energy from the chiller system 54 to the water passing through thefirst subcooler 100 and the first condenser 108 using a refrigerant. Therefrigerant used is not particularly limited. In the present embodiment,the refrigerant used in the first refrigerant circuit 200 is ahaloalkane refrigerant such as R-134a. In other embodiments, therefrigerant can be substituted with another suitable refrigerant such asR-12, R-409A, or R-414A. As shown in FIG. 6, the refrigerant flows in acircuit from the first compressor 216 to the first condenser 108 to thefirst subcooler 100 to first evaporator 208 and back to the firstcompressor 216.

The first evaporator 208 is in thermal communication with the chillersystem 54. The first evaporator 208 is not particularly limited and isgenerally configured to evaporate liquid refrigerant received from thefirst subcooler 100 into a gas. The heat energy required for the phasechange is provided by the waste heat of the chiller system 54. Themanner by which the waste heat from the chiller system is received bythe first evaporator 208 is not particularly limited. In the presentembodiment, the first evaporator 208 is disposed along the path by whichthe waste heat is transferred from the heat transfer unit 66 to thecooling tower 70. It is to be appreciated that by position the firstevaporator 208 in the chiller system 54 as described, at least a portionof the waste heat will be received by the first evaporator 208 and usedtoward evaporating the refrigerant in the first refrigerant circuit 200.In another embodiment, an additional heat transfer mechanism (not shown)can be installed between the chiller system 54 and the heat recoverysystem 62 to transfer the waste heat to the heat recovery system 62. Forexample, a liquid with a high heat capacity can be used to absorb andtransfer the heat energy between the chiller system 54 and the heatrecovery system.

The first compressor 216 is generally configured to move the refrigerantthrough the first refrigerant circuit 200. In addition, the firstcompressor 216 is configured to compress the refrigerant into a hot,high-pressure refrigerant gas for delivery to the first condenser 108.It is to be understood that the first compressor 216 is not particularlylimited. In the present embodiment, the first compressor 216 is a rotaryscrew compressor with a slider for capacity control. However, in otherembodiments, the first compressor 216 can be a reciprocating compressor,a centrifugal compressor, or a scroll compressor with a variable-speedmotor, a two-speed motor or unloaders for capacity control.

The second refrigerant circuit 204 includes the second subcooler 104,the second condenser 112, a second evaporator 212, and a secondcompressor 220. The second refrigerant circuit 204 is generallyconfigured to transfer heat energy from the chiller system 54 to thewater passing through the second subcooler 104 and the second condenser112 using a refrigerant. The refrigerant used is not particularlylimited and can be of the same type of refrigerant as used in the firstrefrigerant circuit. Alternatively, the refrigerant used in the secondrefrigerant circuit 204 can be a different. As shown in FIG. 6, therefrigerant flows in a circuit from the second compressor 220 to thesecond condenser 112 to the second subcooler 104 to second evaporator212 and back to the first compressor 220.

The second evaporator 212 is in thermal communication with the chillersystem 54 similar to the first evaporator 208. The second evaporator 212is not particularly limited and is generally configured to evaporateliquid refrigerant received from the second subcooler 104 into a gas. Itis to be appreciated that the second evaporator 212 is not particularlylimited and can be similar or identical to the first evaporator 208. Itis to be re-emphasized that the present embodiment is a non-limitingembodiment and that the first evaporator 208 and the second evaporator212 can be different from described. For example, the first evaporator208 and the second evaporator 212 can be different sizes, from differentmanufacturers, of a different type.

The second compressor 220 is generally configured to move therefrigerant through the second refrigerant circuit 204. In addition, thesecond compressor 220 is configured to compress the refrigerant into ahot, high-pressure refrigerant gas for delivery to the second condenser112. It is to be understood that the second compressor 220 is notparticularly limited. In the present embodiment, the second compressor220 is a rotary screw compressor with a slider for capacity control.However, in other embodiments, the first compressor 216 can be areciprocating compressor, a centrifugal compressor, or a scrollcompressor with a variable-speed motor, a two-speed motor or unloadersfor capacity control. Furthermore, although the first compressor 216 andthe second compressor 220 are identical in the present embodiment, it isto be understood that either one of the compressors 216, 220 can be adifferent type. In particular, since the parameters of the firstrefrigerant circuit 200 and the second refrigerant circuit 204 aredifferent as discussed below, the first compressor 216 and the secondcompressor 220 can each be independently optimized for the firstrefrigerant circuit 200 and the second refrigerant circuit 204,respectively.

In transferring heat energy at the first condenser 108 and secondcondenser 112, the temperature of the water should optimally be raisedto the temperature at which the refrigerant undergoes the phase changegiving off heat (condensation temperature). It is to be appreciated thatsince the water temperature in the two condensers 108, 112 are not equalto each other, the pressure to which the refrigerant in the firstrefrigerant circuit 200 and the second refrigerant circuit 204 must becompressed will not be equal. Since the temperature to which the waterin the second condenser 112 is to be raised is higher, the pressure towhich the refrigerant in the second refrigerant circuit 204 is raised ishigher.

In the present embodiment, the parameters of the hot water system 58determine the amount that the temperature of the water is to be raised,which ultimately determines the cumulative amount of heat energy addedto the water. In particular, since the water is generally flowing, aheat transfer rate would need to be determined based on the flow rate ofthe water. For example, if the cold water source 116 supplies water atabout 25° C. and the hot water tank 78 is configured to store water at atemperature of about 55° C., then sufficient heat energy is added toraise the temperature of the amount of water by about 30° C. As anotherexample, if the hot water tank 78 is configured to store water at atemperature of about 60° C., sufficient heat energy is added to raisethe temperature of the amount of water by about 35° C. As anotherexample, if the hot water tank 78 is configured to store water at atemperature of about 65° C., sufficient heat energy is added to raisethe temperature of the amount of water by about 40° C. It is to beappreciated that different applications can demand differenttemperatures of water and that some buildings can have a plurality ofwater tanks, each water tank maintaining the temperature of the water ata different temperature.

Since the second refrigeration circuit requires greater compression, itis to be understood that the second compressor 220 compresses therefrigerant to a higher pressure than the first compressor 216. If bothcondensers were required to operate at the higher temperature requiredfor delivery into the hot water tank 78 (such as if the water flows inparallel through the condensers instead of in series), both the firstcompressor 216 and the second compressor 220 would need to operate atthe higher pressure. Accordingly, by providing a two step process, attwo different condensation temperatures in condensers 108, 112, the heatrecovery system 62, only the second compressor 220 compresses therefrigerant to a high pressure. Due to the lower pressure in condenser108, it is to be appreciated, with the benefit of this description, thatless power would be required by the first compressor 216 than the secondcompressor 220 resulting in further energy savings.

Referring to FIG. 7, a refrigerant and water temperature profile isplotted on the same graph as a function of heat transferred for a singlecondenser/subcooler pair during an exemplary operation without directingthe flow of water through the condensers in series. Accordingly, thecondenser is required to operate at a higher pressure such that thecondensation temperature is at about 60° C.

Referring to FIG. 8, a refrigerant and water temperature profile isplotted on the same graph as a function of heat energy transferred forthe heat recovery system 62 where the water is directed through twocondensers in series during an exemplary operation. Accordingly, thefirst condenser can be operated at lower pressure such that thecondensation temperature is at about 50° C. to step up the temperatureof the water. The water is then passed to the second condenser having ahigher condensation temperature to raise the temperature of the water tothe predetermined temperature for delivery into the hot water tank 78.

Referring to FIG. 9, another embodiment of an energy exchange system fortransferring heat energy is shown generally at 50 a. Like components ofthe energy exchange system 50 a bear like reference to theircounterparts in the energy exchange system 50, except followed by thesuffix “a”. The energy exchange system 50 a includes a chiller system 54a, a hot water system 58 a, and a heat recovery system 62 a.

In the present embodiment, the hot water system 58 a includes a hotwater tank 78 a without a boiler. It is to be appreciated, with thebenefit of this description, that the energy exchange system 50 a canoperate without an additional boiler for providing hot water. Inparticular, the waste heat provided by the chiller system 54 a canprovide the heat recovery system 62 a with sufficient heat energy tomeet all the needs of the hot water system 58 a. For example, if theenergy exchange system 50 a were installed in a building where thechiller system 54 a is providing significant waste heat that can meetthe building's need for hot water, a boiler would not be required insuch a building. Examples of such buildings include buildings located inwarm climates where the air conditioning use is high and the hot wateruse is relatively low.

Referring to FIG. 10, a schematic representation showing the flow ofwater through another embodiment of a heat recovery system 62 b isshown. Like components of the heat recovery system 62 b bear likereference to their counterparts in the heat recovery system 62, exceptfollowed by the suffix “b”. The heat recovery system 62 b includes afirst subcooler 100 b, a second subcooler 104 b, a third subcooler 106b, a first condenser 108 b, a second condenser 112 b, and a thirdcondenser 114 b.

In general, the heat recovery system 62 b operates in a similar manneras the heat recovery system 62 with an additional step. By including anadditional step, it is to be appreciated, with the benefit of thisdescription, that additional energy savings can be obtained as the stepsby which the temperature of the water is increased can be smaller.Furthermore, it is to be re-emphasized that this embodiment is anon-limiting representation only. For example, it is to be appreciatedthat the heat recovery system 62 b can include more steps to achieveeven greater energy savings.

Further variations are contemplated. For example, as shown in FIG. 11, aschematic representation showing the flow of water through anotherembodiment of a heat recovery system 62 c is shown. Like components ofthe heat recovery system 62 c bear like reference to their counterpartsin the heat recovery system 62, except followed by the suffix “c”. Theheat recovery system 62 c includes a first subcooler 100 c, a secondsubcooler 104 c, a first condenser 108 c, a second condenser 112 c, anda valve 300 c.

In this embodiment, a valve 300 c is installed in between the watersource 116 c and the first subcooler 100 c. The valve 300 c is generallyconfigured to control the flow of water to the first subcooler 100 c. Itis to be appreciated that the valve 300 c allows the relative amounts ofwater passing through the first subcooler 100 c and the second subcooler104 c to be controlled. Furthermore, during periods of low demand forhot water, the valve 300 c can be shut off and the compressor (notshown) associated with the first condenser 108 c can be powered down toachieve even greater energy savings.

Referring to FIG. 12, a schematic representation showing the flow ofrefrigerant through another embodiment of a heat recovery system 62 d isshown in greater detail. Like components of the heat recovery system 62d bear like reference to their counterparts in the heat recovery system62, except followed by the suffix “d”. In the present embodiment, asingle compressor 218 d is used to compress the refrigerant and a firstvalve 400 d and a second valve 404 d are used to control the pressureand amount of refrigerant flowing to a first condenser 108 d and asecond condenser 112 d.

Further variations, combinations, and subsets of the foregoing will nowoccur to those skilled in the art. For example, the heat recovery system62 b can be combined with the heat recovery system 62 d such that asingle pump is used to control the refrigerant across the threecondensers using valves. As another example, the heat recovery system 62b can be combined with the heat recovery system 62 c such that one ortwo of the condenser/subcooler pairs can be shut down to achieve energysavings.

While specific embodiments have been described and illustrated, suchembodiments should be considered illustrative only and should not serveto limit the accompanying claims.

What is claimed is:
 1. A system for heating water, the systemcomprising: a first subcooler for receiving a first water flow, thefirst subcooler configured to transfer heat to the first water flow at afirst heat transfer rate; a second subcooler for receiving a secondwater flow, the second subcooler configured to transfer heat to thesecond water flow at a second heat transfer rate; a first condenser influid communication with the first subcooler and the second subcooler,the first condenser configured to receive a combined water flow, thecombined water flow including the first water flow from the firstsubcooler and the second water flow from the second subcooler, the firstcondenser configured to transfer heat to the combined water flow at athird heat transfer rate; and a second condenser in fluid communicationwith the first condenser, the second condenser configured to receive thecombined water flow from the first condenser, the second condenserconfigured to transfer heat to the combined water flow at a fourth heattransfer rate.
 2. The system of claim 1, wherein the first subcooler isconfigured to transfer heat from a first refrigerant to the first waterflow and the first condenser is configured to transfer heat from thefirst refrigerant to the combined water flow.
 3. The system of claim 2,wherein the second subcooler is configured to transfer heat from asecond refrigerant to the second water flow and the second condenser isconfigured to transfer heat from the second refrigerant to the combinedwater flow.
 4. The system of claim 3, further comprising a firstevaporator and a second evaporator, the first evaporator for evaporatingthe first refrigerant and the second evaporator for evaporating thesecond refrigerant.
 5. The system of claim 4, wherein at least one ofthe first evaporator and the second evaporator is configured to receivewaste heat from a chiller system.
 6. The system of claim 5, furthercomprising a first connector and a second connector, the first connectorfor connecting a cold water source to the first subcooler and the secondsubcooler to receive the water, the second connector for connecting thechiller system to the evaporator for receiving the waste heat.
 7. Thesystem of claim 6, wherein the second connector is configured to receivea liquid.
 8. The system of claim 4, further comprising a firstcompressor and a second compressor, the first compressor for compressingthe first refrigerant and the second compressor for compressing thesecond refrigerant.
 9. The system of claim 8, wherein the secondcompressor compresses the second refrigerant to a higher pressure thanthe first compressor compresses the first refrigerant.
 10. The system ofclaim 9, wherein the first condenser, the first subcooler, the firstevaporator and the first compressor form a first refrigerant circuit.11. The system of claim 10, wherein the first refrigerant circuit is aclosed circuit.
 12. The system of claim 1, wherein the first portion ofwater is equal to the second portion of water.
 13. The system of claim1, wherein the first heat transfer rate, the second heat transfer rate,the third heat transfer rate, and the fourth heat transfer rate arecumulatively sufficient for increasing a temperature of the combinedwater flow by at least 30° C.
 14. The system of claim 13, wherein thefirst heat transfer rate, the second heat transfer rate, the third heattransfer rate, and the fourth heat transfer rate are cumulativelysufficient for increasing a temperature of the combined water flow by atleast 35° C.
 15. The system of claim 14, wherein the first heat transferrate, the second heat transfer rate, the third heat transfer rate, andthe fourth heat transfer rate are cumulatively sufficient for increasinga temperature of the combined water flow by at least 40° C.
 16. A methodof heating water, the method comprising: receiving, at a firstsubcooler, a first water flow; transferring heat at a first heattransfer rate to the first water flow through the first subcooler;receiving, at a second subcooler, a second the water flow; transferringheat at a second heat transfer rate to the second water flow through thesecond subcooler; receiving, at the first condenser, a combined waterflow, the combined water flow including the first water flow from thefirst subcooler and the second water flow from the second subcooler;transferring heat at a third heat transfer rate to the combined waterflow through the first condenser; receiving, at the second condenser,the combined water flow from the first condenser; and transferring heatat a third heat transfer rate to the combined water flow through thesecond condenser.
 17. The method of claim 16, wherein transferring heatto the first water flow through the first subcooler and transferringheat to the combined water flow through the first condenser comprisestransferring heat from a first refrigerant.
 18. The method of claim 17,wherein transferring the heat to the second water flow through thesecond subcooler and transferring heat to the combined water flowthrough the second condenser comprises transferring heat from a secondrefrigerant.
 19. The method of claim 18, further comprising compressingthe second refrigerant to a higher pressure than the first compressorcompresses the first refrigerant.
 20. The method of claim 16, furthercomprising increasing a temperature of the water by at least 30° C. bytransferring heat to the first water flow through the first subcooler,transferring heat to the second water flow through the second subcooler,transferring heat to the combined water flow through the firstcondenser, and transferring heat to the combined water flow through thesecond condenser.